Pump

ABSTRACT

The present invention is directed to providing a pump capable of achieving improvement of a discharge efficiency. A pump configured to suck and discharge fluid includes a housing, a driving shaft rotatably supported on the housing, and a pump element contained in the housing and configured to be rotated by the driving shaft. The housing contains therein an intake passage into which the fluid delivered from outside the housing is introduced, an intake port configured to guide the fluid from the intake passage to the pump element, a discharge port into which the fluid pressurized by the pump element is introduced, and a discharge passage configured to discharge the fluid delivered from the discharge port to outside the housing. The discharge passage includes a first passage including a beginning portion connected to the discharge port and a termination portion. The first passage extends as far as the termination portion around one straight line. The discharge passage further includes a second passage connected to the termination portion of the first passage and opened to outside the housing. A shape of the first passage in cross section taken along a direction perpendicular to the straight line changes continuously from the beginning portion to the termination portion.

TECHNICAL FIELD

The present invention relates to a pump.

BACKGROUND ART

Conventionally, there has been known a pump configured to suck and discharge fluid. For example, PTL 1 discloses a pump including a housing, a shaft rotatably supported on the housing, and a pump element contained in the housing and coupled with the above-described shaft. An intake passage for introducing the fluid from outside the housing into the pump element, and a discharge passage for discharging the fluid pressurized by the pump element to outside the housing are provided inside the housing of this pump.

CITATION LIST Patent Literature

[PTL 1] Japanese Patent Application Public Disclosure No. 2016-142220

SUMMARY OF INVENTION Technical Problem

The conventional pump entails a risk of a reduction in the discharge efficiency of the pump due to a discontinuous change in the cross-sectional shape of the discharge passage.

Solution to Problem

In a pump according to one aspect of the present invention, a discharge passage includes a first passage and a second passage. The first passage extends around one straight line. A shape of the first passage in cross section taken along a direction perpendicular to this straight line changes continuously from a beginning portion to a termination portion. The second passage is connected to the termination portion of the first passage, and is opened to outside the housing.

Therefore, the pump can improve the discharge efficiency thereof.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a circuit of a hydraulic oil supply system of an engine according to a first embodiment.

FIG. 2 is a perspective view of a balancer module with a pump according to the first embodiment mounted thereon.

FIG. 3 is a side view of the balancer module with the pump according to the first embodiment mounted thereon.

FIG. 4 illustrates a cross section as viewed along a line IV-IV in FIG. 3.

FIG. 5 is a front view of the pump according to the first embodiment.

FIG. 6 illustrates a cross section as viewed along a line VI-VI in FIG. 5.

FIG. 7 is a perspective view in which the pump according to the first embodiment is disassembled and each component is lined along the same axis.

FIG. 8 is a front view of the pump with a cover removed therefrom according to the first embodiment.

FIG. 9 is a front view of a housing main body according to the first embodiment.

FIG. 10 illustrates a cross section as viewed along a line X-X in FIG. 9.

FIG. 11 is a bottom view of the housing main body according to the first embodiment.

FIG. 12 illustrates a discharge port and the vicinity thereof in the front view of the housing main body according to the first embodiment in an enlarged manner.

FIG. 13 illustrates a cross section as viewed along a line XIII-XIII in FIG. 11.

FIG. 14 illustrates a cross section as viewed along a line XIV-XIV in FIG. 11.

FIG. 15 illustrates a cross section as viewed along a line XV-XV in FIG. 11.

FIG. 16 illustrates a cross section as viewed along a line XVI-XVI in FIG. 9.

FIG. 17 is a schematic view of a discharge passage according to the first embodiment, and indicates a flow of oil with arrows.

FIG. 18 is a schematic view of the discharge passage according to another embodiment, and indicates the flow of the oil with arrows.

FIG. 19 is a front view of the pump according to a second embodiment.

FIG. 20 illustrates a cross section as viewed along a line XX-XX in FIG. 19.

FIG. 21 illustrates a cross section as viewed along a line XXI-XXI in FIG. 19.

DESCRIPTION OF EMBODIMENTS

In the following description, embodiments for implementing the present invention will be described with reference to the drawings.

First Embodiment

First, a configuration will be described. A pump 1 according to the present embodiment is used for a hydraulic oil supply system of an internal combustion engine (an engine) of an automobile. The engine is a reciprocating engine, and is an in-line multi-cylinder (for example, four-cylinder) engine. The pump 1 is an oil pump that supplies oil (hydraulic oil) in the form of fluid to each sliding portion and a variable actuation valve mechanism of the engine. The variable actuation valve mechanism is a valve timing controller or the like, and controls an actuation characteristic of a valve in the engine. The pump 1 is a source that generates a hydraulic pressure for lubrication and actuation of the variable actuation valve mechanism. As illustrated in FIG. 1, the hydraulic oil supply system of the engine includes an oil pan 100, oil passages, the pump 1, a pressure sensor 18, and a control mechanism. The oil pan 100 is located at a lower portion of the engine, and is a low-pressure portion in which the hydraulic oil is stored. The passages include an intake passage 11, a discharge passage 12, a relief passage 13, and a main gallery 14. One end of the intake passage 11 is connected to the oil pan 100 via an oil strainer 101. The other end of the intake passage 11 is connected to an intake port 110 of the pump 1. One end of the discharge passage 12 is connected to a discharge port 120 of the pump 1. The other end of the discharge passage 12 is connected to an oil filter 102. The relief passage 13 branches off from the discharge passage 12, and can discharge the hydraulic oil to the oil pan 100. A relief valve 16 is mounted in the relief passage 13. One end of the main gallery 14 is connected to the oil filter 102. The main gallery 14 can supply the hydraulic oil to each sliding portion of the engine, the variable actuation valve device, and the like. The pressure sensor 18 is mounted in the main gallery 14. The pressure sensor 18 detects a pressure (a main gallery pressure) P1 in the main gallery 14.

The control mechanism includes a control passage 15, a control valve 17, and an engine control unit 19. The control valve 17 is an electromagnetic valve (a solenoid valve) including a valve portion and a solenoid portion, and is a proportional control valve. The valve portion is a three-way valve. The valve portion is a spool valve, and includes a housing, a spool as a valve body, and a spring as a return spring. The housing includes an inlet port 171, a pilot port 172, a discharge port 173, and an outlet port 174. The spring biases the spool toward an initial position. A pressure (a pilot pressure) of the oil supplied from the pilot port 172 to inside the housing biases the spool in a direction opposite from the spring. The solenoid portion generates an electromagnetic force, and biases the spool in the direction opposite from the spring. The solenoid portion can continuously change strength of the electromagnetic force according to a value of a supplied current. The control passage 15 includes a supply passage 151, a feedback passage 152, a discharge passage 153, and a communication passage 154. The supply passage 151 branches off from the main gallery 14, and is connected to the inlet port 171 of the control valve 17. The feedback passage 152 branches off from the supply passage 151, and is connected to the pilot port 172 of the control valve 17. The discharge passage 153 is connected to the discharge port 173 of the control valve 17, and is in communication with the oil pan 100. The communication passage 154 connects the output port 174 of the control valve 17 and a control chamber 80 of the pump 1 to each other.

As illustrated in FIGS. 2 to 4, the pump 1 is mounted in a balancer module (a balancer unit) 2 of the engine. In other words, the balancer module 2 is a pump-integrated balancer. The balancer module 2 is a balancer mechanism for canceling out a secondary vibration generated at the engine, and generates a vibratory force in a direction for canceling out the above-described vibration by balancer shafts 25 and 26 rotating in synchronization with a crankshaft. The module 2 includes a housing, the balancer shafts 25 and 26, and a gear. The housing includes a lower housing 200 and an upper housing 201. In the following description, a three-dimensional orthogonal coordinate system is set in the drawings for the sake of the description. A z-axis is set to a direction in which axes of the balancer shafts 25 and 26 extend, and a positive side thereof is defined to be the pump 1 side with respect to the balancer shafts 25 and 26. An x-axis is set to a horizontal direction perpendicular to the z-axis, and a positive side thereof is defined to be the driving-side shaft 25 side with respect to the driven-side shaft 26. A y-axis is set to a vertical direction (an upright direction) perpendicular to the z-axis, and a positive side thereof is defined to be the upper housing 201 side with respect to the lower housing 200. The z-axis direction extends horizontally and the y-axis direction extends vertically with the engine mounted on the vehicle (the automobile). The y-axis positive direction is located on a vertically upper side, and the x-axis negative direction is located on a front side of the vehicle. The layout of the engine on the vehicle is not limited thereto.

As illustrated in FIG. 4, the lower housing 200 includes gear containing portions, bearing containing portions, and weight containing portions. Each of the containing portions has a semi-cylindrical shape extending in the z-axis direction, and is opened on a surface of the lower housing 200 on the y-axis positive direction side. The gear containing portions include a driving gear containing portion 211, a driving-side inverting gear containing portion 212, a driven-side inverting gear containing portion 213, a reducing gear containing portion 214, and a pump driving gear containing portion 215. The bearing containing portions include a driving-side first bearing containing portion 221, a driving-side second bearing containing portion 222, a driven-side first bearing containing portion 223, and a driven-side second bearing containing portion 224. The weight containing portions include a driving-side weight containing portion 231 and a driven-side weight containing portion 232. The driving gear containing portion 211, the driving-side first bearing containing portion 221, the driving-side weight containing portion 231, the driving-side second bearing containing portion 222, and the driving-side inverting gear containing portion 212 are arranged in this order from the z-axis positive direction side toward the z-axis negative direction side on one axis of the lower housing 200 on the x-axis positive direction side. The reducing gear containing portion 214, the driven-side first bearing containing portion 223, the driven-side weight containing portion 232, the driven-side second bearing containing portion 224, and the driven-side inverting gear containing portion 213 are arranged in this order from the z-axis positive direction side toward the z-axis negative direction side on one axis of the lower housing 200 on the x-axis negative direction side. The pump driving gear containing portion 215 is located adjacent to the driving gear containing portion 211 on the z-axis positive direction side at an end of the lower housing 200 in the z-axis positive direction and a center of the lower housing 200 in the x-axis direction. The pump driving gear containing portion 215 and the reducing gear containing portion 214, the driving-side first bearing containing portion 221 and the driven-side first bearing containing portion 223, the driving-side weight containing portion 231 and the driven-side weight containing portion 232, the driving-side second bearing containing portion 222 and the driven-side second bearing containing portion 224, and the driving-side inverting gear containing portion 212 and the driven-side inverting gear containing portion 213 are located adjacent to each other in the x-axis direction, respectively. A bolt hole 241 penetrating through the lower housing 200 in the y-axis direction is located adjacent to each of the bearing containing portions in the x-axis direction.

The upper housing 201 includes gear containing portions, bearing containing portions, weight containing portions, and a mounting portion 242. Each of the containing portions is shaped and laid out substantially identically to the corresponding containing portion in the lower housing 200, and is opened to a surface of the upper housing 201 on the y-axis negative direction side. The driving gear containing portion 211 is also opened on a surface of the upper housing 201 on the y-axis positive direction side. The upper housing 201 is fixed to the lower housing 200 with use of a bolt 202 penetrating through the bolt hole 241 of the lower housing 200. A surface of the lower housing 200 on the y-axis positive direction side and the surface of the upper housing 201 on the y-axis negative direction side are joined to each other, by which the gear containing portions, the bearing containing portions, and the weight containing portions are completed. The mounting portion 242 is a protrusion portion protruding from the surface of the upper housing 201 on the y-axis positive direction side, and includes a bolt hole extending in the y-axis direction. The balancer module 2 is mounted on a lower portion (a y-axis negative direction side) of the cylinder block so as to hang down with use of a bolt 203 penetrating through the bolt hole of the mounting portion 242. The balancer module 2 is contained in the oil pan 100.

The balancer shafts include the driving-side shaft 25 and the driven-side shaft 26. The driving-side shaft 25 and the driven-side shaft 26 are disposed in parallel with the crankshaft. Both the shafts 25 and 26 are sandwiched between the upper housing 201 and the lower housing 200, are arranged adjacent to each other in an xz plane, and are rotatably supported on both the housings 200 and 201. These shafts 25 and 26 include balancer weights 250 and 260, respectively. The weights 250 and 260 are each an eccentric weight having a center of gravity offset from the axes of these shafts 25 and 26. The gears include a balancer driving gear 27, inverting gears, and a reducing gear 29. The inverting gears include a driving-side inverting gear 281 and a driven-side inverting gear 282. The balancer driving gear 27 is fixed to an end of the driving-side shaft 25 in the z-axis positive direction. The driving-side inverting gear 281 is fixed to an end of the driving-side shaft 25 in the z-axis negative direction. The driven-side inverting gear 282 is fixed to an end of the driven-side shaft 26 in the z-axis negative direction. The reducing gear 29 is fixed to an end of the driven-side shaft 26 in the z-axis positive direction. They are fixed by press-fitting or the like.

The balancer weight 250 of the driving-side shaft 25 is contained in the driving-side weight containing portion 231 of both the housings 200 and 201. The balancer driving gear 27 is contained in the driving gear containing portion 211 of both the housings 200 and 201. The driving-side inverting gear 281 is contained in the driving-side inverting gear containing portion 212 of both the housings 200 and 201. A journal portion of the driving-side shaft 25 between the balancer weight 250 and the balancer driving gear 27 is supported by a bearing 251 contained in the driving-side first bearing containing portion 221 of both the housings 200 and 201. A journal portion between the balancer weight 250 and the driving-side inverting gear 281 is supported by a bearing 252 contained in the driving-side second bearing containing portion 222 of both the housings 200 and 201. The balancer weight 260 of the driven-side shaft 26 is contained in the driven-side weight containing portion 232 of both the housings 200 and 201. The reducing gear 29 is contained in the reducing gear containing portion 214 of both the housings 200 and 201. The driven-side inverting gear 282 is contained in the driven-side inverting gear containing portion 213 of both the housings 200 and 201. A journal portion of the driven-side shaft 26 between the balancer weight 260 and the reducing gear 29 is supported by a bearing 261 contained in the driven-side first bearing containing portion 223 of both the housings 200 and 201. A journal portion between the balancer weight 260 and the driven-side inverting gear 282 is supported by a bearing 262 contained in the driven-side second bearing containing portion 224 of both the housings 200 and 201. A part of an outer periphery of the balancer driving gear 27 protrudes from an opening portion of the upper housing 201 toward the y-axis positive direction side, and is meshed with a gear integrated with the crankshaft. A gear ratio of the balancer driving gear 27 is set in such a manner that the driving-side shaft 25 rotates twice as fast as the number of rotations of the crankshaft. The driven-side inverting gear 282 is meshed with the driving-side inverting gear 281. Both the shafts 25 and 26 rotate in opposite directions from each other at the same number of rotations.

As illustrated in FIGS. 5 to 8, the pump 1 is a variable displacement-type vane pump. The pump 1 includes a housing 3, bolts 30, a pump driving gear 400, a driving shaft 4, a rotor 5, a plurality of vanes 6, vane rings 61 and 62, a cam ring 7, a seal member 71, a pin 72, and a spring 73. The housing 3 includes a housing main body (a body) 300 and a cover 301.

As illustrated in FIGS. 9 to 11, the housing main body 300 includes a pump element containing portion 31, a spring containing portion 32, passage portions, and a flange portion 35. A bearing portion 360, a pin hole 361, a pump element containing hole 362, a spring containing hole 363, an intake port 110, a discharge port 120, an intake passage 11, a discharge passage 12, and a communication passage 154 are provided inside the housing main body 300. The pump element containing portion 31 has a bottomed cylindrical shape, and includes a bottom portion 310 and a cylindrical circumferential wall 311. The pump element containing hole 362, the bearing portion 360, the pin hole 361, the intake port 110, and the discharge port 120 are provided in the pump element containing portion 31. The pump element containing hole 362 is a bottomed cylindrical recessed portion extending in the z-axis direction. The hole 362 is closed on the z-axis positive direction side by the bottom portion 310, and is opened on the z-axis negative direction side on a surface of the housing main body 300 on the z-axis negative direction side. The bearing portion 360 extends around an axis 40 in the z-axis direction, and penetrates through a generally central position of the bottom portion 310. The pump element containing hole 362 extends around the axis 40. The pin hole 361 has a bottomed cylindrical shape extending in the z-axis direction, and is opened on the surface of the bottom portion 310 on the z-axis negative direction side (a bottom surface 364 of the pump element containing hole 362 in the z-axis direction). The pin hole 361 is located an outer edge of the bottom surface 364 on the x-axis positive direction side and the y-axis positive direction side. The intake port 110 and the discharge port 120 are arcuate recessed portions extending in the direction around the axis 40 (hereinafter referred to as a circumferential direction), and are opened on the surface of the bottom portion 310 on the z-axis negative direction side (the bottom surface 364 of the pump element containing hole 362). The intake port 110 is bottomed. The intake port 110 is located between the bearing portion 360 and the pin hole 361 on the bottom surface 364. The discharge port 120 is located on the pin hole 361 side with respect to the bearing portion 360. A straight line passing through the axis 40 and the pin hole 361 (a central axis thereof) overlap both the ports 110 and 120. These ports 110 and 120 are located on opposite sides of a straight line extending perpendicular to this straight line and passing through the axis 40 from each other.

As illustrated in FIGS. 10 and 12, the discharge port 120 extends around a first straight line 91 inside the bottom portion 310. The first straight line 91 extends in parallel with the axis 40, and extends along the axis 40 (in the z-axis direction). The first straight line 91 passes through a circumferentially intermediate position of the opening of the discharge port 120 on the bottom surface 364. A cross section of the discharge port 120 taken along a direction perpendicular to the first straight line 91 has a circumferentially elongated flattened shape. A dimension of the discharge port 120 in the circumferential direction is larger than a dimension of the discharge port 120 in a radial direction of the driving shaft 4. A wall 121 on a rotational direction side of the driving shaft 4, among walls forming an inner periphery of the discharge port 120, extends along the radial direction of the driving shaft 4 and is also slightly inclined with respect to the first straight line 91, and is gradually displaced toward an opposite rotational direction side of the driving shaft 4 as extending from the negative direction side toward the positive direction side of the z-axis. A wall 122 on the opposite rotational direction side of the driving shaft 4 extends along the radial direction of the driving shaft 4 and is also inclined with respect to the first straight line 91, and is gradually displaced toward the rotational direction side of the driving shaft 4 as extending from the negative direction side toward the positive direction side of the z-axis. A wall 123 on an inner side in the radial direction of the driving shaft 4 extends along the circumferential direction and is also slightly inclined with respect to the first straight line 91, and is gradually displaced toward an outer side in the radial direction as extending from the negative direction side toward the positive direction side of the z-axis. A wall on the outer side in the radial direction includes a portion 124 bulging inward in the radial direction near the pin hole 361. A portion 125 of the wall on the outer side in the radial direction on the opposite rotational direction side of the driving shaft 4 with respect to the above-described bulging portion 124 extends along the circumferential direction. A portion 126 on the rotational direction side of the driving shaft 4 with respect to the above-described bulging portion 124 has a so-called pent roof-like shape, and includes a portion slightly bulging outward in the radial direction with respect to a circular arc γ. The circular arc γ is a circular arc centered at the axis 40, and passing through an end on the outer side in the radial direction that is one of beginning portions of the discharge port 120 (in the circumferential direction). Further, the walls 124, 125, and 126 on the outer side in the radial direction are slightly inclined with respect to the first straight line 91, and are gradually displaced inward in the radial direction as extending from the negative direction side toward the positive direction side of the z-axis.

As illustrated in FIG. 9, the spring containing portion 32 is located on a y-axis negative direction side of the pump element containing portion 31. The spring containing portion 32 includes the intake passage 11 and the spring containing hole 363. The intake passage 11 and the spring containing hole 363 are opened on the surface of the housing 300 on the z-axis negative direction side. The intake passage 11 is opened on the circumferential wall 311 of the pump element containing hole 362, and is connected to the intake port 110. The intake passage 11 extends from the intake port 110 toward the x-axis negative direction side and the y-axis negative direction side. The spring containing hole 363 has a cylindrical shape extending generally along the x-axis direction, and intersects with the intake passage 11.

The passage portions include a discharge passage portion 33 and a communication passage portion 34. As illustrated in FIGS. 10 and 11, the discharge passage portion 33 extends in the x-axis positive direction from a y-axis positive direction side of a surface of the pump element containing portion 31 (the bottom portion 310) on the z-axis positive direction side. The discharge passage portion 33 includes a main body portion 330, a first bulging portion 331, and a second bulging portion 332. The discharge passage portion 33 is a plate-like flattened portion extending along the xz plane. Dimensions of the main body portion 330 in the x-axis direction and the z-axis direction are larger than a dimension of the main body portion 330 in the y-axis direction. Bolt holes 333 are provided at the bulging portions 331 and 332. The bolt holes 333 extend in the y-axis direction and penetrate through the bulging portions 331 and 332. The first bulging portion 331 overlaps the main body portion 330 on an x-axis negative direction side and a z-axis negative direction side of the discharge passage portion 33, and is connected to the bottom portion 310. The second bulging portion 332 overlaps the main body portion 330 on an x-axis positive direction side and a z-axis positive direction side of the discharge passage portion 33, and is connected to a z-axis positive direction side of the bottom portion 330. An x-axis positive direction side of the discharge passage portion 33 extends in the z-axis direction. As viewed from the y-axis direction, an x-axis negative direction side of the discharge passage portion 33 has such a shape that a large circular arc of the main body portion 330 is sandwiched by small circular arcs of the bulging portions 331 and 332, and extends while being inclined with respect to the x-axis and the z-axis. A surface of the discharge passage portion 33 on the y-axis negative direction side is in parallel with the xz plane. A surface of the discharge passage portion 33 on the y-axis positive direction side is slightly inclined with respect to the xz plane, and is gradually displaced toward the y-axis negative direction side as extending from the negative direction side toward the positive direction side of the z-axis.

The discharge passage 12 includes a first passage 12A and a second passage 12B. Both the passages 12A and 12B are located inside the main body portion 330. As illustrated in FIGS. 12 to 16, the first passage 12A has a beginning portion 12A1 connected to the discharge port 120, and extends as far as a termination portion 12A2 around a second straight line 92. The second straight line 92 is in parallel with the axis 40 of the driving shaft 4, and extends along the axis 40 (in the z-axis direction). The second straight line 92 passes through a circumferentially intermediate position of the first passage 12A. A cross section of the first passage 12A taken along a direction perpendicular to the second straight line 92 has a flattened shape elongated in the circumferential direction. A dimension of the first passage 12A in the circumferential direction is larger than a dimension of the first passage 12A in the radial direction of the driving shaft 4. The first passage 12A (the second straight line 92) is eccentric toward the rotational direction side of the driving shaft 4 with respect to the discharge port 120 (the first straight line 91). A wall 127 on the rotational direction side of the driving shaft 4, among walls forming an inner periphery of the first passage 12A, extends along the y-axis direction and is also slightly inclined with respect to the first straight line 91, and is gradually displaced toward the opposite rotational direction side of the driving shaft 4 as extending from the negative direction side toward the positive direction side of the z-axis. A curved surface portion 127A is provided on a z-axis negative direction side of the wall 127, and this curved surface portion 127A is smoothly continuously connected to the wall 121 of the discharge port 120. A wall 128 on the opposite rotational direction side of the driving shaft 4 has a curved surface-like shape convexed toward the opposite rotational direction of the driving shaft 4, and is also smoothly (via a curved surface) continuously connected to the wall 122 of the discharge port 120 on the opposite rotational direction side of the driving shaft 4. The surface 128 is slightly inclined with respect to the first straight line 91, and is gradually displaced toward the rotational direction side of the driving shaft 4 (the x-axis positive direction side) as extending from the negative direction side toward the positive direction side of the z-axis. A wall on the inner side in the radial direction of the driving shaft 4 extends along the circumferential direction, and an end portion 123A thereof on the opposite rotational direction side of the driving shaft 4 also partially extends in the x-axis direction. The end portion 123A is continuously connected to the wall 122 of the discharge port 120 smoothly (via a curved surface). The other portion forms the same plane as the wall 123 of the discharge port 120 on the inner side in the radial direction of the driving shaft 4. The walls 123 and 123A on the inner side in the radial direction of the driving shaft 4 are slightly inclined with respect to the first straight line 91, and are gradually displaced outward in the radial direction as extending from the negative direction side toward the positive direction side of the z-axis. The wall on the outer side in the radial direction of the driving shaft 4 forms the same plane as the walls 124 and 126 of the discharge port 120 on the outer side in the radial direction of the driving shaft 4. The end portion (the beginning portion) 124 of the radially outer wall on the opposite rotational direction side of the driving shaft 4 bulges inward in the radial direction near the pin hole 361. A portion 126 not including this bulging portion 124 has a so-called pent roof-like shape, and includes a portion slightly bulging outward in the radial direction with respect to the above-described circular arc γ. Further, the walls 124 and 125 on the outer side in the radial direction are slightly inclined with respect to the first straight line 91, and are gradually displaced inward in the radial direction as extending from the negative direction side toward the positive direction side of the z-axis. A wall 129 at an end in the z-axis positive direction extends perpendicularly to the z-axis. Each of the portions 127, 128, and 129, and the like of the wall forming the inner periphery of the first passage 12A is continuously connected to each other smoothly (via a curved surface).

In this manner, the shape of the first passage 12A in cross section taken along the direction perpendicular to the second straight line 92 changes continuously from the beginning portion 12A1 to the termination portion 12A2 of the first passage 12A. The shape of a connection portion between the beginning portion 12A1 and the discharge port 120 in cross section perpendicular to the axis 40 changes continuously between the beginning portion 12A1 and the discharge port 120. The cross-sectional area of this connection portion gradually reduces as the connection portion extends from the discharge port 120 toward the beginning portion 12A1 (as the connection portion extends from the negative direction side to the positive direction side along the z-axis). The cross-sectional area of the first passage 12A gradually reduces as the first passage 12A extends from the beginning portion 12A1 toward the termination portion 12A2 (as the first passage 12A extends from the negative direction side to the positive direction side along the z-axis).

The second passage 12B is connected to the termination portion 12A2 of the first passage 12A, and extends around a third straight line 93 (along a third straight line 93) to be opened to outside the housing 3. The third straight line 93 extends in the y-axis direction. The second passage 12B is opened on the surface of the main body portion 330 on the y-axis negative direction side. This opening is located at a position away from the bottom portion 310 (the end of the driving shaft 4 in the z-axis positive direction) by a predetermined distance in the axial direction of the driving shaft 4 (the z-axis direction). A cross section of the second passage 12B taken along a direction perpendicular to the third straight line 93, including the above-described opening, is circular. The area of the opening of the second passage 12B at the termination portion 12A2 of the first passage 12A is equal to or smaller than a cross-sectional area of the first passage 12A taken at a portion α of this opening that is closest to the beginning portion 12A1 (the end in the z-axis negative direction, refer to FIG. 11), and is equal to or larger than a cross-sectional area of the first passage 12A taken at a farthest portion β of the above-described opening from the beginning portion 12A1 (the end in the z-axis positive direction). A member such as a pipe and the oil filter 102 is connected to the opening of the second passage 12B that is opened to outside the housing 3. Bolts penetrate through the bolt holes 333 of both the bulging portions 331 and 332. The bulging portions 331 and 332 function as fixation portions for fixing the member connected to the above-described opening of the second passage 12B together with the above-described bolts.

As illustrated in FIGS. 9 and 11, the communication passage portion 34 extends in the x-axis positive direction from an outer surface of the pump element containing portion (the circumferential wall 311) on the x-axis positive direction side and the y-axis positive direction side. The communication passage portion 34 includes a main body portion 340 and boss portions 341 and 342. Bolt holes 343 are provided at the boss portions 341 and 342. The bolt holes 343 extend in the y-axis direction, and penetrate through the boss portions 341 and 342. The communication passage 154 is provided inside the communication passage portion 34. A beginning portion of the communication passage 154 is opened on a surface on the y-axis negative direction side at an end portion of the main body portion 340 on the x-axis positive direction side. A member connected to the control valve 17 is connected to the opening of the communication passage 154. The boss portions 341 and 342 function as fixation portions for fixing the above-described member connected to the control valve 17. A termination portion of the communication passage 154 is opened on an inner peripheral surface of the pump element containing hole 362.

As illustrated in FIG. 9, the flange portion 35 is located on the z-axis negative direction side of the housing main body 300, and surrounds the openings of the pump element containing hole 362 and the intake passage 11 (the spring containing hole 363). Three first boss portions 351, three second boss portions 352, and one pin hole 354 are provided at the flange portion 35. A bolt hole 353 is provided at each of the boss portions 351 and 352. The bolt hole 353 extends in the z-axis direction and penetrates through the boss portion 351 or 352. The pin hole 354 extends in the z-axis direction and penetrates through the flange portion 35. The three first boss portions 351 are arranged around the pump containing hole 362 in such a manner that the axis 40 of the driving shaft 4 is interposed between them in the x-axis direction and is also interposed between them in the y-axis direction on a y-axis positive direction side of the flange portion 35. The three second boss portions 352 are arranged around the spring containing hole 363 in such a manner that the axis 40 is interposed between them in the x-axis direction on a y-axis negative direction side of the flange portion 35.

As illustrated in FIG. 7, the cover 301 includes an intake passage portion 37, an oil strainer mounting portion 38, a relief passage portion 39, and the flange portion 35. The bearing portion 360, the pin hole 361, the intake port 110, the discharge port corresponding groove 365, the intake passage 11, and the relief passage 13 are provided inside the cover 301. The bearing portion 360, the pin hole 361, the intake port 110, the discharge port corresponding groove 365, and the intake passage 11 are opened on a surface of the cover 301 on the z-axis positive direction side while being positioned and shaped in correspondence with the bearing portion 360, the pin hole 361, the intake port 110, the discharge port 120, and the intake passage 11 of the housing main body 300 in the z-axis direction, respectively. The bearing portion 360 penetrates through the cover 301 in the z-axis direction. The pin hole 361 has a bottomed cylindrical shape extending in the z-axis direction. The intake port 110 and the discharge port corresponding groove 365 are bottomed recessed portions. The intake passage 11 is located inside the intake passage portion 37. One end of the intake passage 11 is connected to the intake port 110. The other end side of the intake passage 11 extends in the z-axis direction and is connected to the oil strainer mounting portion 38. The oil strainer 101 is mounted in the oil strainer mounting portion 38. The relief passage portion 39 extends in the x-axis negative direction and the y-axis negative direction from the outer surface of the cover 301 on the x-axis negative direction side and the y-axis positive direction side. The relief passage 13 is located inside the relief passage portion 39. A beginning portion of the relief passage 13 is opened on an inner peripheral surface of the discharge port corresponding groove 365. A termination portion of the relief passage 13 is opened on the outer surface of the cover 301. The relief valve 16 is mounted in the relief passage 13. The relief valve 16 includes a ball 160 as a valve body, a spring 161 as a return spring, and a retainer 162 of the spring 161. The flange portion 35 is located on a z-axis positive direction side of the cover 301. The boss portions 351 and 352, and the pin hole 354 are provided on the flange portion 35 at positions corresponding to the boss portions 351 and 352 and the pin hole 354 of the housing main body 300 in the z-axis direction, respectively. Another boss portion 352 is provided at the relief passage portion 39. Bolt holes 353 are provided at the boss portions 351 and 352. Further, another pin hole 355 is provided at the flange portion 35. The bolt holes 353 extend in the z-axis direction and penetrate through the boss portions 351 and 352. The pin hole 355 extends in the z-axis direction and penetrates through the flange portion 35.

As illustrated in FIGS. 6 and 8, the rotor 5, the plurality of vanes 6, the vane rings 61 and 62, the cam ring 7, the seal member 71, and the pin 72 are mounted in the pump element containing hole 362. The spring 73 is mounted in the spring containing hole 363. The z-axis positive direction side of the driving shaft 4 is fitted to the bearing portion 360 of the housing main body 300, and is rotatably supported. The z-axis negative direction side of the driving shaft 4 is fitted to the bearing portion 360 of the cover 301, and is rotatably supported. An intermediate portion of the driving shaft 4 in the z-axis direction is located in the pump element containing hole 362. Pluralities of grooves 41 and protrusion portions 42 extending along the axial direction of the driving shaft 4 are provided on an outer periphery of the intermediate portion of the driving shaft 4. A flange portion 43 is provided at the end of the driving shaft 4 in the z-axis positive direction. The flange portion 43 can restrict a movement of the driving shaft 4 relative to the housing main body 300 toward the z-axis negative direction side. The end portion of the driving shaft 4 in the z-axis negative direction protrudes from the cover 301 toward the z-axis negative direction side. The pump driving gear 400 is fixed at this end portion by press-fitting or the like. The pump driving gear 400 is meshed with the reducing gear 29 of the balancer module 2. The rotor 5 is columnar. Pluralities of grooves 51 and protrusion portions 52 extending along the axis of the rotor 5 are provided on an inner periphery of the rotor 5. The protrusion portions 42 (the grooves 41) of the driving shaft 4 are fitted to the grooves 51 (the protrusion portions 52) of the rotor 5. In other words, the driving shaft 4 and the rotor 5 are coupled axially relatively movably due to splines. Recessed portions 53 are provided on both sides of the rotor 5 in the z-axis direction. The vane rings 61 and 62 are mounted in the recessed portions 53. A plurality of (seven) radially extending slits 54 is provided inside the rotor 5. Radially outer sides of the slits 54 are opened on an outer peripheral surface 50 of the rotor 5. Back-pressure chambers 55 are connected to radially inner sides of the slits 54. The back-pressure chambers 55 are cylindrical, and extend in the z-axis direction and penetrate through the rotor 5. The vanes 6 are contained in the slits 54. A proximal end of each of the vanes 6 faces the vane ring 61 or 62.

Both ends of the pin 72 are fitted to the pin hole 361 of the housing main body 300 and the pin hole 361 of the cover 301, respectively. An inner peripheral surface 700 of the cylinder 7 is cylindrical. A pin groove 74, a seal groove 75, and an arm portion 76 are provided on an outer periphery of the cam ring 7. The pin groove 74 is semi-cylindrical, and extends in the z-axis direction and penetrates through the cam ring 7. A part of the outer periphery of the pin 72 is fitted in the pin groove 74. The seal member 71 is mounted in the seal groove 75. The arm portion 76 is a plate-like portion, and protrudes from the outer periphery of the cam ring 7 radially outward. The arm portion 76 is mounted on an x-axis positive direction side of the spring containing hole 363. A surface of the arm portion 76 on the x-axis positive direction side can contact the protrusion 321 located on the x-axis positive direction side of the spring containing hole 363. A plurality of grooves 77 is provided on both surfaces of the cam ring 7 in the z-axis direction. Each of the grooves 77 is shaped generally identically to the intake port 110 or the discharge port 120 (the discharge port corresponding groove 365) of the housing 3 that faces it in the z-axis direction, and is connected to the inner peripheral side of the cam ring 7. The grooves 77 have a function of adjusting a force derived from a pressure applied to the cam ring 7 from the both sides in the z-axis direction. The spring 73 is a compression coil spring. One end of the spring 73 is set on a surface of the arm portion 76 on the x-axis negative direction side. The other end of the spring 73 is set on an inner peripheral surface of the spring containing hole 363 on the x-axis negative direction side. An axis of the spring 73 is approximately perpendicular to a straight line connecting an axis of the pin 72 and the surface of the protrusion 321 on the x-axis negative direction side in an xy plane. The spring 73 is kept in a compressed state and has a predetermined set load in an initial state where the cam ring 7 is not actuated (does not swing), thereby constantly biasing the arm portion 76 toward the x-axis positive direction side.

The control chamber 80 is located between the inner surface of the housing 3 and the outer periphery of the cam ring 7. The control chamber 80 is a space surrounded by a portion of the outer peripheral surface 701 of the cam ring 7 between the seal member 71 and the pin 72 (one side not including the arm portion 76), the inner surface of the pump element containing hole 362, and the surface of the cover 301 on the z-axis positive direction side. The control chamber 80 is sealed by the seal member 71 and the pin 72. The communication passage 154 is opened to the control chamber 80.

Pump chambers (vane chambers) 81 are separated and formed (defined) by the outer peripheral surface 50 of the rotor 5, the two vanes 6 adjacent to each other, the inner peripheral surface 700 of the cam ring 7, the bottom surface 364 of the pump containing chamber 362, and the surface of the cover 301 on the z-axis positive direction side. When the rotor 5 rotates, the vanes 6 project from and retract into the outer peripheral surface 50 of the rotor 5 in such a manner that distal ends of the vanes 6 contact the inner peripheral surface 700 of the cam ring 7. The volumes of the vane chambers 81 can change according to the rotation of the rotor 5, and a pump function is exerted with the aid of increases and reductions in the volumes of the vane chambers 81 according to the rotation. The intake port 110 is opened to the vane chambers 81 in a range where the volumes of the vane chambers 81 increase (according to the rotation of the rotor 5) (an intake region). The vane chambers 81 in the intake region suck the oil from the intake port 110. The discharge port 120 is opened to the vane chambers 81 in a range where the volumes of the vane chambers 81 reduce (according to the rotation of the rotor 5) (a discharge region). The vane chambers 81 in the discharge region discharge the oil to the discharge port 120. The rotation of the crankshaft is transmitted to the balancer shafts 25 and 26 via the gear 27 and the like. The rotations of the balancer shafts 25 and 26 are transmitted to the driving shaft 4 of the pump 1 via the gears 29 and 40. The gear ratios of the gears 29 and 40 are set in such a manner that the driving shaft 4 rotates half as fast as the number of rotations of the driven-side shaft 26. As a result, the number of rotations of the driving shaft 4 matches the crankshaft.

The driving shaft 4 rotates the rotor 5 in a counterclockwise direction in FIG. 8. The components forming the pump chamber such as the rotor 5 and the vanes 6 (pump elements) pressurize the oil introduced from the intake port 110 and introduce it to the discharge port 120 by rotating. The axis 40 of the driving shaft 4 coincides with rotational axes of the pump elements. The direction around the axis 40 is the rotational direction of the driving shaft 4, i.e., rotational directions of the pump elements. A pressure at the discharge port 120 is introduced into the back-pressure chambers 55. As a result, the vanes 6 are pushed out from the slits 54. Even when the number of rotations is low and the centrifugal force and the pressures in the back-pressure chambers 55 are low, the vane rings 61 and 62 push out the vanes 6 from the slits 54. Due to this configuration, the liquid tightness of the vane chambers 81 is improved. Further, a stress, like a stress that would be generated when the driving shaft 4 is press-fitted in the rotor 5, is not generated on the rotor 5 because of the spline fitting between the driving shaft 4 and the rotor 5. Therefore, the pump 1 can prevent such a situation that the rotor 5 is broken due to the slits 54 spread out by the hydraulic pressures that the vanes 6 receive when the rotor 5 rotates. The pump 1 sucks the oil from the oil pan 100 via the intake passage 11 and discharges the oil to the discharge passage 12. The pump 1 pressure-feeds the hydraulic oil to each portion of the engine via the main gallery 14 connected to the discharge passage 12. The relief valve 16 is opened and discharges the oil from the discharge passage 12 via the relief passage 13, when a pressure in the discharge passage 12 (a discharge pressure) reaches a predetermined high pressure.

A theoretical discharge amount (a discharge amount per rotation), i.e., a capacity of the pump 1 is determined based on a difference between a maximum volume and a minimum volume of each of the vane chambers 81. This volume difference (a change amount of the volume of the vane chamber 81) is changeable. The cam ring 7 is a member capable of moving (a movable member) inside the pump containing hole 362, and can swing around the pin 72 in the rotational direction. The swing of the cam ring 7 causes a change in the difference between the central axis 40 of the rotor 5 and a central axis 78 of the cam ring inner peripheral surface 700 (an eccentricity amount). The change in the eccentricity amount causes a change in an increase/reduction amount of the volume (the volume change amount) of each of the plurality of vane chambers 81 when the rotor 5 rotates. The cam ring 7 is biased by the spring 73 toward one side in a direction of the rotation around the pin 72 (which is the counterclockwise direction in FIG. 8 and is one side that leads to the increase in the eccentricity amount and the increase in the volume change amount of each of the plurality of vane chambers 81). Assume that Fs represents this spring force. The oil supplied from the discharge port 120 to the main gallery 14 can be introduced into the control chamber 80 via the control passage 15. The cam ring 7 receives the pressure of the oil contained in the control chamber 80. The cam ring 7 is biased by the above-described hydraulic pressure toward the other side in the direction of the rotation around the pin 72 (which is a clockwise direction in FIG. 8 and is the other side that leads to the reduction in the eccentricity amount and the reduction in the volume change amount of each of the plurality of vane chambers 81). Assume that Fp represents a force due to this hydraulic pressure (a hydraulic force). The position of the cam ring 7 in the rotational direction (the eccentricity amount, i.e., the capacity) is determined mainly based on Fp and Fs. When Fp exceeds Fs, the cam ring 7 swings toward the above-described other side in the rotational direction, and the eccentricity amount (the capacity) reduces. When Fp falls below Fs, the cam ring 7 swings toward the above-described one side in the rotational direction, and the eccentricity amount (the capacity) increases.

The control valve 17 can control the introduction of the oil into the control chamber 80 and the discharge of the oil from the control chamber 80. When the spool is located at the initial position, the communication between the outlet port 174 (the communication passage 154) and the inlet port 171 (the supply passage 151) is blocked, and the communication between the outlet port 174 and the discharge port 173 (the discharge passage 153) is established. As a result, the oil can be discharged from inside the control chamber 80 of the pump 1 via the communication passage 154 and the discharge passage 153. When the spool moves from the initial position in the direction opposite from the biasing force of the spring, the communication between the outlet port 174 and the discharge port 173 is blocked, and the communication between the outlet port 174 and the inlet port 171 is established. As a result, the oil can be supplied from the main gallery 14 to inside the control chamber 80 via the supply passage 151 and the communication passage 154. The pressure in the main gallery 14 is applied to the spool as a pilot pressure via the feedback passage 152. As a result, the position of the spool is subjected to feedback control, and the eccentricity amount (the volume) is adjusted. In other words, when the pressure in the main gallery 14 (the pilot pressure) increases, the spool moves in the direction opposite from the biasing force of the spring. This movement causes the oil to be supplied to the control chamber 80 to increase the pressure in the control chamber 80, thereby increasing Fp and reducing the eccentricity amount. On the other hand, when the pressure in the main gallery 14 (the pilot pressure) reduces, the spool moves in the same direction as the biasing force of the spring. This movement causes the oil to be discharged from the control chamber 80 to reduce the pressure in the control chamber 80, thereby reducing Fp and increasing the eccentricity amount. A repetition of them allows the pressure in the main gallery 14 to be kept at a constant value (within a predetermined range around the constant value).

The solenoid portion changes the pressure in the main gallery 14 when the spool starts moving by changing the strength of the electromagnetic force. The electromagnetic force assists the pilot pressure by biasing the spool in the direction opposite from the spring. Therefore, according to an increase in the electromagnetic force, the spool moves in the direction opposite from the biasing force of the spring and causes a start of the oil supply to the control chamber 80 with a further low pressure in the main gallery 14 (the pilot pressure). As a result, the pressure in the main gallery 14 is controlled to a further low constant value (within a predetermined range around the constant value). The engine control unit 19 calculates the required pressure in the main gallery 14 according to driving conditions, such as the number of rotations of the engine, a load, and an oil temperature and a water temperature. The control unit 19 changes the value of the current to supply to the solenoid portion (the strength of the electromagnetic force) based on information input from the pressure sensor 18 and the like and a built-in program. Due to this mechanism, the control unit 19 can perform feedback control on the pressure in the main gallery 14 to the above-described required value. The control unit 19 can control the pressure in the main gallery 14 continuously, so to speak, in a non-step manner. Therefore, the pump 1 can achieve, for example, improvement of fuel efficiency of the vehicle.

Next, a procedure of manufacturing the pump 1 will be described. The manufacturing procedure includes a first process of casting the housing main body 300 and the cover 301, a second process of machining the housing main body 300 and the cover 301, a third process of mounting the pump elements (the rotor 5 and the like) into the pump element containing hole 362 of the housing main body 300, and a fourth process of joining the cover 301 and the housing main body 300 to each other. In the first process, the housing main body 300 is cast by die-casting of an aluminum alloy. Three dies are used. After molten metal is poured, a “first die for forming the discharge passage portion 33 and the like together with the pump element containing portion 31” is removed toward one side in the axial direction of the driving shaft 4 (the z-axis positive direction side). A “second die for forming the pump element containing hole 362 and the discharge port 120 inside the pump element containing portion 31 and also forming the first passage 12A inside the discharge passage portion 33” is removed toward the other side in the axial direction of the driving shaft 4 (the z-axis negative direction side). A “third die for forming the second passage 12B in the discharge passage portion 33” is removed in the axial direction of the second passage 12B (the y-axis negative direction side) with respect to the discharge passage portion 33. Work of removing the second die is easy, because the pump 1 is configured in such a manner that the surface of the discharge passage portion 33 on the y-axis positive direction side is gradually displaced to the y-axis negative direction side as extending toward the one side in the axial direction of the driving shaft 4 (the z-axis positive direction side) while the surface of the discharge passage position 33 on the y-axis negative direction side is in parallel with the xz plane. Work of removing the second die is easy, because the pump 1 is configured in such a manner that the cross-sectional areas of the first passage 12A and the discharge port 120 gradually reduce as they extend toward the one side in the axial direction of the driving shaft 4 (the z-axis positive direction side). Further, work of removing the third die is easy, because the pump 1 is configured in such a manner that the second passage 12B is opened on the surface of the discharge passage portion 33 on the one side (the surface on the y-axis negative direction side). The second process includes machining the bearing portion 360, the surface of the discharge passage portion 33 on the y-axis negative direction side, and the inner peripheral surface of the second passage 12B in the housing main body 300. Processing (burring) the surface of the discharge passage portion 33 on the y-axis negative direction side and the inner peripheral surface of the second passage 12B can contribute to improvement of connectability (sealability and the like) of the member to the opening of the second passage 12B.

The fourth process includes attaching the cover 301 to the surface of the housing main body 300 on the z-axis negative direction side at the first boss portions 351 with use of the bolts 30. The pins 356 can be inserted into both the pin holes 354 and 354, which allows the cover 301 to be positioned relative to the housing main body 300. The cover 301 is integrated with the housing main body 300 by being fastened by the bolts 30. The surface of the cover 301 on the z-axis positive direction side closes the opening of the pump element containing hole 362. In a process of mounting the pump 1 onto the balancer module 2, the cover 301 of the housing 3 is joined to the lower housing 200 or the upper housing 201 of the balancer module 2, or is joined to both the housings 200 and 201 while extending across them. The housing 3 is attached to the front end surface of the housing 200 (201) (the surface on the z-axis positive direction side) at the second boss portions 352 of the housing main body 300 and the second boss portions 352 of the cover 301 with use of the bolts 30. The bolts 30 also have a function of fastening the boss portions 352 to 352 to each other. The pin 357 can be inserted into the pin hole 355, which allows the housing 3 to be positioned relative to the balancer module 2.

Next, advantageous effects will be described. The beginning portion 12A1 of the first passage 12A of the discharge passage 12 is connected to the discharge port 120. The first passage 12A extends as far as the termination portion 12A2 around the second straight line 92. The second passage 12B is connected to the termination portion 12A2, and is opened to outside the housing 3. The second passage 12B functions as the discharge port that is located at the termination portion of the discharge passage 12 and is used to discharge the fluid out of the housing 3. As illustrated in FIG. 18, in a case where the discharge passage 12 is shaped in such a manner that the shape of the passage in cross section taken along the direction perpendicular to the axis of the flow passage discontinuously changes, i.e., there is an orthogonal step on the inner wall of the passage, a swirl might be generated at this step. This would undesirably result in an increase in a pressure loss inside the pump 1 and thus a reduction in the discharge efficiency. The reduction in the discharge efficiency of the pump 1 would also lead to deterioration of the fuel efficiency. As illustrated in FIG. 17, in the present embodiment, the shape of the first passage 12A in cross section taken along the direction perpendicular to the second straight line 92 changes continuously from the beginning portion 12A1 to the termination portion 12A2. In other words, there is no portion that discontinuously changes (the orthogonal step) in the direction in which the first passage 12A extends (the axial direction of the flow passage) on the inner wall of the first passage 12A (including the beginning portion 12A1 and the termination portion 12A2). Therefore, the pump 1 can prevent the pressure loss that otherwise would be caused by the step (the generation of the swirl therefrom). In this manner, the “continuous” change means that the change is not intermittent, and the cross-sectional shape of the passage gradually (smoothly) changes along the flow passage instead of sharply changing. The rate of the above-described change does not necessarily have to be constant. Further, the first passage 12A may partially include a section where the cross-sectional shape is kept constant.

The above-described cross-sectional area of the first passage 12A reduces as the first passage 12A extends from the beginning portion 12A1 toward the termination portion 12A2 (from the beginning portion 12A1 to the termination portion 12A2). Therefore, the pump 1 can prevent a reduction in the flow speed in the first passage 12A. The above-described cross-sectional area of the first passage 12A gradually reduces as the first passage 12A extends from the beginning portion 12A1 toward the termination portion 12A2. In other words, the first passage 12A gradually reduces in cross-sectional area as extending from the beginning portion 12A1 toward the termination portion 12A2. As a result, the pump 1 prevents a sharp change in the cross-sectional area in the first passage 12A (including the beginning portion 12A1 and the termination portion 12A2). Therefore, the pump 1 can prevent the pressure loss because causing no sharp change in the flow speed and thus preventing occurrence of a turbulent flow. The rate of the above-described reduction does not necessarily have to be constant. Further, the first passage 12A may partially include a section where the cross-sectional area is kept constant. Even when there is a portion where the cross-sectional shape discontinuously changes, the advantageous effects can be maintained as long as this change is sufficiently small.

The cross-sectional shape of the discharge port 120 changes continuously as the discharge port 120 extends from the pump element (the vane chambers 81) side toward the beginning portion 12A1 of the first passage 12A. Further, the above-described cross-sectional area of the discharge port 120 gradually reduces as the discharge port 120 extends from the pump element side toward the beginning portion 12A1. Therefore, the above-descried advantageous effects similar to the first passage 12A can also be acquired at the discharge port 120. Similarly, the cross-sectional shape of the connection portion between the discharge port 120 and the beginning portion 12A1 of the first passage 12A changes continuously between the discharge port 120 and the beginning portion 12A1. In other words, the pump 1 can prevent the pressure loss due to the step because there is no portion that changes discontinuously in the axial direction of the flow passage on the inner wall of this connection portion. Further, the pump 1 can prevent the pressure loss due to the change in the cross-sectional area because the cross-sectional area of the above-described connection portion gradually reduces as the connection portion extends from the discharge port 120 toward the beginning portion 12A1. It can be deemed that the discharge passage 12 starts from an arbitrary position of the discharge port 120 in the z-axis direction, and it can also be deemed that the discharge port 120 continues as far as an arbitrary position of the beginning portion 12A1 of the discharge passage 12 in the z-axis direction.

The housing 3 includes the housing main body 300 and the cover 301. The housing main body 300 includes the discharge port 120, the first passage 12A, and the second passage 12B. In other words, the discharge port 120, the first passage 12A, and the second passage 12B are formed integrally with the housing main body 300. This eliminates the necessity of mounting a seal member for improving the liquid tightness between the discharge port 120 and the first passage 12A and between the first passage 12A and the second passage 12B, thereby being able to prevent an increase in the number of components, complication of the structure, and the like. Further, this integration can further facilitate realization of the configuration in which the above-described cross-sectional shapes of the connection portion between the discharge port 120 and the first passage 12A and the first passage 12A continuously change (or the cross-sectional areas gradually reduce).

The above-described cross-sectional area of the first passage 12A before it reaches the second passage 12B is equal to or larger than the area of the second passage 12B in cross section perpendicular to the third straight line 93. Therefore, the pump 1 can achieve a smooth flow of the fluid in the first passage 12A and thus create an efficient flow by securing the cross-sectional area of the first passage 12A. The area of the opening of the second passage 12B at the termination portion 12A2 of the first passage 12A is equal to or smaller than the cross-sectional area of the first passage 12A taken at the portion α of this opening that is closest to the beginning portion 12A1, and is equal to or larger than the cross-sectional area of the first passage 12A taken at the farthest portion β of the above-described opening from the beginning portion 12A1. In other words, the cross-sectional area of the termination portion 12A2 of the first passage 12A is substantially equal to the area of the above-described opening of the second passage 12B. Therefore, the pump 1 can prevent the pressure loss due to the change in the cross-sectional area because succeeding to prevent the sharp change in the cross-sectional area of the flow passage at the connection portion between these passages 12A and 12B.

In a case where there is a plurality of bent points of the flow passage in the passage including the discharge passage 12 from the pump elements to outside the housing 3 (the opening thereto), such a configuration would undesirably result in an increase in the pressure loss due to generation of a swirl at the bent points and thus a reduction in the discharge efficiency. Further, this configuration might lead to increases in the number of processes and the cost for forming the passage. This configuration would necessitate machining processing from a plurality of directions to form one passage by connecting a plurality of (linear) passages, thereby leading to an increase in the number of processing procedures. A seal plug would become necessary to close an opening to outside the housing 3 that would be generated at the time of the processing. As a result, the number of components and the number of assembling processes would increase, also leading to an increase in the weight. In the present embodiment, the first passage 12A extends around the second straight line 92, and the second passage 12B extends around the third straight line 93 (along the third straight line 93). In this manner, the first passage 12A and the second passage 12B each extend linearly. Therefore, there is only one bent point of the flow passage in the discharge passage 12 at most (one bent point between the first passage 12A and the second passage 12B). The pump 1 can prevent the pressure loss due to the bent passage (the generation of the swirl due to that) because succeeding to maximumly reduce the number of bent points. Further, the pump 1 can reduce the number of processes and the cost for forming the discharge passage 12. The same also applies to the example in which there is the step on the inner wall as illustrated in FIG. 18. Further, the discharge port 120 extends around the first straight line 91, and the first straight line 91 extends in parallel with the second straight line 92. Therefore, the pump 1 can also reduce the number of bent points between the discharge port 120 and the first passage 12A.

The second straight line 92 does not necessarily have to extend along the axis 40 of the driving shaft 4. In other words, the first passage 12A may extend around a straight line that is not in parallel with the axis 40. In the case of the present embodiment, the first passage 12A (the second straight line 92) extends along the axis 40 (in parallel with the axis 40). Therefore, the pump 1 can prevent an increase in the dimension of the housing 3 in the radial direction of the driving shaft 4. Similarly, the first straight line 91 does not necessarily have to extend along the axis 40. In the case of the present embodiment, the discharge port 120 (the first straight line 90) extends along the axis 40. Therefore, the pump 1 can prevent the increase in the dimension of the housing 3 in the radial direction of the driving shaft 4.

The housing main body 300 includes the pump element containing hole 362. The pump element containing hole 362 is the recessed portion that contains the pump elements. The cover 301 closes the opening of the pump element containing hole 362. The pump element containing hole 362 has the bottomed cylindrical shape extending around the axis 40 of the driving shaft 4, and the discharge port 120 is opened on the bottom surface 364 of the pump element containing hole 362 in the axial direction of the driving shaft 4. Therefore, the pump 1 can prevent the increase in the dimension of the housing main body 300 in the radial direction of the driving shaft 4, compared to when the discharge port 120 is opened on the circumferential wall 311 of the pump element containing hole 362. Further, the first passage 12A extending along the axis 40 is opened on the bottom surface 364 of the pump element containing hole 362 via the discharge port 120, which facilitates the formation of the first passage 12A together with the pump element containing hole 362 by the casting. Further, the present configuration causes the fluid guided from the pump elements to the discharge port 120 to mainly flow in the direction along the axis 40 inside the discharge port 120. This is the same as the direction in which the fluid flows in the first passage 12A (the axial direction of the flow passage). Therefore, the pump 1 can prevent generation of a bent point of the flow passage at the connection portion between the discharge port 120 and the first passage 12A (the beginning portion 12A1).

The dimension of the discharge port 120 (extending along the axis 40 of the driving shaft 4) is larger in the rotational direction of the driving shaft 4 than in the radial direction of the driving shaft 4. In other words, the cross section of the discharge port 120 perpendicular to the first straight line 91 (in parallel with the rotational axis of the pump elements) has the flattened shape elongated in the rotational direction of the pump elements. Therefore, the pump 1 can secure the above-described cross-sectional area of the discharge port 120 while preventing the increase in the dimension of the housing 3 in the radial direction of the driving shaft 4, thereby achieving improvement of the discharge efficiency. Similarly, the dimension of the first passage 12A (extending along the axis 40 of the driving shaft 4) is larger in the rotational direction of the driving shaft 4 than in the radial direction of the driving shaft 4. In other words, the cross section of the first passage 12A perpendicular to the second straight line 92 (in parallel with the rotational axis of the pump elements) has the flattened shape elongated in the rotational direction of the pump elements. Therefore, the pump 1 can secure the above-described cross-sectional area of the first passage 12A while preventing the increase in the dimension of the housing 3 in the radial direction of the driving shaft 4, thereby achieving improvement of the discharge efficiency. Now, the above-descried cross section of the first passage 12A and the above-described cross section of the discharge port 120 are shaped similarly to each other (the flattened shape), which can further facilitate the realization of the configuration in which the cross-sectional shape of the connection portion between the discharge port 120 and the first passage 12A (the beginning portion 12A1) continuously changes (or the cross-sectional area thereof gradually changes).

The first passage 12A (the second straight line 92) is eccentric toward the rotational direction side of the driving shaft 4 with respect to the discharge port 120 (the first straight line 91). Therefore, the pump 1 can improve the discharge efficiency thereof. More specifically, the amount of the fluid guided from the pump elements to the discharge port 120 is greater on the rotational direction side (the termination side of the discharge port 120) than on the opposite rotational direction side (the beginning side of the discharge port 120) of the driving shaft 4. Further, the fluid guided from the pump elements to the discharge port 120 and flowing inside the discharge port 120 includes a component in the rotational direction of the driving shaft 4 (inertial energy in the rotational direction). The first passage 12A (the center thereof) is eccentric toward the rotational direction side of the driving shaft 4 with respect to the discharge port 120 (the center thereof), which allows the fluid to be efficiently guided from the pump elements to the first passage 12A via the discharge port 120. Further, the first passage 12A easily receives the inertial energy in the rotational direction, and therefore the pressure loss can be reduced. The center of the discharge port 120 (the first straight line 91) may be a center of the discharge port 120 in cross section taken at an arbitrary position in the z-axis direction without being limited to the center of the opening, or may be an averaged position of these centers.

At least a part in the rotational direction of the driving shaft 4 in the wall on the outer side in the radial direction of the driving shaft 4, among the walls forming the inner periphery of the discharge port 120, is located on the outer side in the radial direction of the driving shaft 4 with respect to the circular arc γ that is the circular arc centered at the axis 40 of the driving shaft 4 and passes through the end on the outer side in the radial direction of the driving shaft 4 in the beginning portion of the discharge port 120 in the rotational direction of the driving shaft 4. In other words, the outer side of the discharge port 120 in the radial direction of the driving shaft 4 bulges outward with respect to the above-described circular arc γ. Therefore, the pump 1 can achieve improvement of the discharge efficiency and the manufacturing efficiency. More specifically, the amount of the fluid guided from the pump elements to the discharge port 120 is greater on the outer side than on the inner side in the radial direction of the driving shaft 4. Further, the fluid guided from the pump elements to the discharge port 120 and flowing inside the discharge port 120 contains a component directed outward in the radial direction of the driving shaft 4 (inertial energy in the radial direction). The discharge port 120 bulges outward in the radial direction, which allows the fluid to be efficiently guided from the pump elements to the first passage 12A via the discharge port 120. Further, the discharge port 120 easily receives the inertial energy in the radial direction, and therefore the pressure loss can be reduced. More specifically, a part of the wall 126 on the rotational direction side of the driving shaft 4, among the walls on the outer side in the radial direction of the discharge port 120, is located on the outer side in the radial direction with respect to the above-described circular arc γ. In other words, the wall bulges more largely radially outward on the rotational direction side (the termination side of the discharge port 120) than on the opposite rotational direction side (the beginning side of the discharge port 120) of the driving shaft 4. Therefore, the pump 1 can further efficiently guide the fluid from the pump elements to the first passage 12A via the discharge port 120, thereby receiving the inertial energy. Further, the discharge port 120 bulges in the radial direction, which contributes to an increase in the area of the opening of the discharge port 120 (the area of the discharge port 120 as viewed from the axial direction of the driving shaft 4) in the housing 3 (the bottom surface 364 of the pump element containing hole 362). Therefore, the discharge port 120 can be easily formed by the casting. In terms of this effect, the discharge port 120 may bulge radially inward. The first passage 12A also bulges radially outward at a part of the wall 126 on the outer side in the radial direction, similarly to the discharge port 120. Therefore, the above-described advantageous effects can also be achieved with respect to the first passage 12A. The fluid can be efficiently guided from the pump elements to the first passage 12A via the discharge port 120, and the first passage 12A easily receives the inertial energy of the fluid. Therefore, the first passage 12A can be easily formed by the casting.

The first passage 12A is located inside the discharge passage portion 33. The discharge passage portion 33 is the plate-like flattened portion. Therefore, when the above-described cross section of the first passage 12A has the flattened shape, the pump 1 can reduce the thickness around the first passage 12A, thereby achieving a reduction in the size of the housing 3 and compactness thereof. The advantageous effects of the present invention can be brought about as long as at least a part of the first passage 12A is located inside the discharge passage portion 33. In the present embodiment, the first passage 12A is approximately entirely located inside the discharge passage portion 33. Therefore, the above-described advantageous effects can be maximized. The second passage 12B is located inside the discharge passage portion 33. The second passage 12B is opened on the surface of the discharge passage portion 33 on the one side (the y-axis negative direction side). Therefore, the pump 1 can achieve a reduction in the length of the second passage 12B, i.e., the dimension from the first passage 12A (the termination portion 12A2) to the above-described opening of the second passage 12B. The pump 1 can reduce the resistance in the flow passage (the pressure loss) by shortening the second passage 12B. The third straight line 93 extends perpendicularly to the second straight line 92 (in the y-axis direction). Therefore, the pump 1 can effectively shorten the second passage 12B when the above-described surface of the discharge passage portion 33 on the one side extends along the second straight line 92 (the xz plane). Further, the pump 1 allows the first passage 12A and the second passage 12B to be easily formed. Further, the pump 1 can prevent an increase in the size of the housing 3 in the direction of the second straight line 92 (the axial direction of the driving shaft 4) due to the second passage 12B.

The bolt hole 333 is provided at the discharge passage portion 33. The bolt for fixing the member connected to the above-described opening of the second passage 12B to the discharge passage portion 33 penetrates through the hole 333. The bulging portions 331 and 332 around the holes 333 function as boss portions. Therefore, a part of the discharge passage portion 33 can be used as the boss portion (the fixation portion for fixing the member), and therefore the boss portion (the fixation portion) does not have to be additionally prepared on the housing 3. As a result, the pump 1 can achieve the reduction in the size of the housing 3 and the compactness thereof.

The second passage 12B perpendicular to the third straight line 93 is circular in cross section. Therefore, the pump 1 can reduce a pressure loss (a frictional loss on the wall surface) in the second passage 12B. Further, circularly shaping the above-described cross section of the second passage 12B can facilitate circularly shaping the opening of the second passage 12B on the outer surface of the housing 3. Circularly shaping the above-described opening can facilitate securing the continuity of an external member to the passage.

The second passage 12B is opened to outside the housing 3 at the position away from the driving shaft 4 in the axial direction of the driving shaft 4 (the z-axis direction). Therefore, the pump 1 can prevent interference between the member connected to the above-described opening of the second passage 12B and the driving shaft 4, thereby facilitating the connection of the member. The second passage 12B is opened to outside the housing 3 on the driving shaft 4 side (the y-axis negative direction side) with respect to the first passage 12A. Therefore, the pump 1 can further effectively acquire the above-described advantageous effects. The end portion of the driving shaft 4 (in the z-axis negative direction) opposite from the end portion of the driving shaft 4 (in the z-axis positive direction) in proximity to the above-described opening of the second passage 12B in the axial direction of the driving shaft 4 protrudes from the housing 3, and power is transmitted from the driving source thereto. In other words, the above-described end portion on the opposite side is connected to the member for driving the driving shaft 4. Therefore, the pump 1 can ensure design flexibility. In other words, the pump 1 can prevent interference between the member connected to the above-described opening of the second passage 12B and the member for driving the driving shaft 4. Further, the size and the position of the above-described opening of the second passage 12B, i.e., the length of the first passage 12A can be set freely according to the prevention of this interference. More specifically, the first passage 12A is formed at a location deep (in the axial direction of the driving shaft 4) enough to form the discharge port having the predetermined size (the opening of the second passage 12B). This depth can be reduced. In other words, the pump 1 allows the above-described opening of the second passage 12B to have a large area while preventing an increase in the dimension of the housing 3 in the axial direction of the driving shaft 4.

The housing 3 (the flange portion 35) includes the first boss portion 351, and the second boss portion 352 located at the different position from the first boss portion 351. The bolt 30 for coupling the cover 301 with the housing main body 300 penetrates through the first boss portion 351. The bolt 30 for coupling the housing 3 with another member (the housings 200 and 201 of the balancer module 2) penetrates through the second boss portion 352. Therefore, the assembling of the pump 1 and the mounting thereof (to another member) can be realized with use of the different boss portions (fixation portions) 351 and 352, respectively, which contributes to improvement of workability of the assembling and the mounting. The pump 1 includes two or more first boss portions 351 (three in the present embodiment). Therefore, the cover 301 and the housing main body 300 can be coupled with each other with improved strength. The first boss portions 351 are arranged around the pump containing hole 362 in such a manner that the axis 40 of the driving shaft 4 is interposed between them in the x-axis direction and the y-axis direction. Therefore, the pump elements can be further firmly held. The pump 1 includes two or more second boss portions 352 (three in the present embodiment). Therefore, the housing 3 (the pump 1) can be attached to another member (the balancer module 2) with improved strength. The second boss portions 352 are disposed opposite of the axis 40 from each other in the x-axis direction. Therefore, the pump 1 can be further firmly mounted. The above-described coupling may be realized with use of a fixation portion based on welding or the like without being limited to the combination of the boss portion and the bolt.

The method for manufacturing the pump 1 includes the first process of integrally forming the housing main body 300 by the casting. Due to the manufacturing using the casting, the “discharge port 120 opened to the pump element containing hole 362, which is the recessed portion capable of rotatably containing the pump elements, extending along the rotational axis 40 of the pump elements, and shaped in such a manner that the cross section thereof perpendicular to the axis 40 has the flattened shape elongated in the rotational direction of the pump elements” and the “first passage 12A extending along the rotational axis 40 of the pump elements and shaped in such a manner that the cross section thereof perpendicular to the axis 40 has the flattened shape elongated in the rotational direction of the pump elements” can be easily formed integrally with the “pump element containing hole 362”. The present manufacturing method can omit the machining process, and also eliminate the necessity of the sealing plug. Further, due to the employment of the casting, the present manufacturing method can easily realize the configuration in which the cross-sectional shapes of the discharge port 120, the connection portion between the discharge port 120 and the first passage 12A, and the first passage 12A continuously change (or the cross-sectional areas thereof gradually reduce). For example, integrally forming the discharge port 120 and the first passage 12A both having the flattened shapes in cross section with use of the same (the second) die facilitates continuously (smoothly) shaping the inner walls of these portions 120 and 12A. Especially, the present manufacturing method can easily realize the configuration in which the cross-sectional areas of the discharge port 120 and the first passage 12A gradually reduce due to a draft angle of the (second) die.

Second Embodiment

First, a configuration will be described. As illustrated in FIGS. 19 to 21, the discharge passage portion 33 includes the main body portion 330, a second passage portion 334, a first boss portion 335, and a second boss portion 336. The main body portion 330 is the same as the first embodiment. The second passage portion 334 is cylindrical, and extends in the x-axis negative direction from the x-axis negative direction side of the main body portion 330. The first passage 12A is located inside the main body portion 330, and the second passage 12B is located inside the second passage portion 334. The first passage 12A is configured identically to the first embodiment. The second passage 12B is cylindrical, and extends in the x-axis direction (perpendicularly to the second straight line 92). The second passage 12B is opened on the wall of the first passage 12A on the x-axis negative direction side, and is also opened on the surface of the second passage portion 334 on the x-axis negative direction side. The first boss portion 335 has a plate-like shape extending from the end of the second passage portion 334 in the x-axis negative direction toward the y-axis positive direction side and the z-axis negative direction side, and extending along a yz plane. The second boss portion 336 is connected to the y-axis negative direction side and the z-axis positive direction side of the end of the second passage portion 334 in the x-axis negative direction, and is located opposite of the second passage portion 334 from the first boss portion 335. A bolt hole 337 is provided at each of the boss portions 335 and 336. The bolt hole 337 of the first boss portion 335 extends in the x-axis direction and penetrates through the first boss portion 335. The bolt hole 337 of the second boss portion 336 has a bottomed shape extending in the x-axis direction. The boss portions 335 and 336 function as the fixation portions for fixing the member connected to the opening of the second passage 12B together with the bolts. The other configuration is similar to the first embodiment.

In the present embodiment, the second passage 12B extends in the x-axis direction, thereby being opened on the outer surface of the housing 3 at a horizontal position to the first passage 12A. Therefore, the pump 1 can improve layout flexibility of the member connected to the above-described opening of the second passage 12B, i.e., layout flexibility of the pump 1 to the above-described member. Besides them, the second embodiment can acquire similar advantageous effects to the first embodiment by a similar configuration to the first embodiment.

Other Embodiments

Having described the embodiments for implementing the present invention with reference to the drawings, the specific configuration of the present invention is not limited to the embodiments, and the present invention also includes a design modification and the like thereof made within a range that does not depart from the spirit of the present invention, if any. Further, the individual components described in the claims and the specification can be arbitrarily combined or omitted within a range that allows them to remain capable of achieving at least a part of the above-described objects or producing at least a part of the above-described advantageous effects. For example, the power transmission mechanism that transmits the rotation of the crankshaft to the balancer shaft (the driving-side shaft) is not limited to the mechanism based on the meshed gears, and may be, for example, a mechanism based on a sprocket or a chain. The target member to which the pump (the housing) is attached is not limited to the balancer module, and may be, for example, the cylinder block. The pump may be employed for a hydraulic oil supply system of a brake apparatus, a power steering apparatus, or the like without being limited to the engine. The pump is not limited to the vane pump, and may be, for example, a gear pump. Further, the pump may be a fixed displacement pump. The specific method for casting the housing main body may be any method. The casting is not limited to the die-casting, and may be casting using a sand mold. The material of the housing main body is not limited to the aluminum alloy, and may be another material.

[Other Configurations Recognizable from Embodiments]

In the following description, other configurations recognizable from the above-described embodiments will be described.

(1) A pump configured to suck and discharge fluid, according to one configuration thereof, includes a housing, a driving shaft rotatably supported on the housing, and a pump element contained in the housing and configured to be rotated by the driving shaft. The housing contains therein an intake passage to which the fluid is introduced from outside the housing, an intake port configured to guide the fluid from the intake passage to the pump element, a discharge port to which the fluid is introduced after being pressurized by the pump element, and a discharge passage configured to discharge the fluid delivered from the discharge port to outside the housing. The discharge passage includes a first passage including a beginning portion connected to the discharge port and a termination portion while extending as far as the termination portion around one straight line, and a second passage connected to the termination portion of the first passage. The second passage is opened to outside the housing. A shape of the first passage in cross section taken along a direction perpendicular to the straight line continuously changes from the beginning portion to the termination portion. (2) According to another configuration, in the above-described configuration, a cross-sectional shape of a connection portion between the discharge port and the beginning portion changes continuously between the discharge port and the beginning portion. (3) According to another configuration, in any of the above-described configurations, the straight line extends along an axis of the driving shaft. (4) According to further another configuration, in any of the above-described configurations, the housing includes a housing main body including a recessed portion. The recessed portion is a bottomed cylindrical recessed portion extending around an axis of the driving shaft, and contains the pump element. The housing further includes a cover closing an opening of the recessed portion. The discharge port is opened on a bottom surface of the recessed portion in an axial direction of the driving shaft. (5) According to further another configuration, in any of the above-described configurations, the discharge port extends along an axis of the driving shaft. (6) According to further another configuration, in any of the above-described configurations, a dimension of the discharge port in a rotational direction of the driving shaft is larger than a dimension of the discharge port in a radial direction of the driving shaft. A dimension of the first passage in the rotational direction of the driving shaft is larger than a dimension of the first passage in the radial direction of the driving shaft. (7) According to further another configuration, in any of the above-described configurations, the first passage is disposed on a front side in the rotational direction of the driving shaft with respect to the discharge port. (8) According to further another configuration, in any of the above-described configurations, at least a part of a wall on an outer side in the radial direction of the driving shaft, among walls forming an inner periphery of the discharge port, is located on the outer side in the radial direction of the driving shaft with respect to a circular arc. The circular arc is centered at the axis of the driving shaft. The circular arc passes through an end on the outer side in the radial direction of the driving shaft in the beginning portion of the discharge port in the rotational direction of the driving shaft. (9) According to further another configuration, in any of the above-described configurations, the housing includes a plate-like flattened portion. A part of the first passage and the second passage are located inside the flattened portion. The second passage is opened on a surface of the flattened portion on one side. A fixation portion for fixing a member connected to an opening of the second passage is provided at the flattened portion. (10) According to further another configuration, in any of the above-described configurations, the second passage is opened to outside the housing at a position away from the driving shaft in the axial direction of the driving shaft. (11) According to further another configuration, in any of the above-described configurations, a second end portion of the driving shaft on an opposite side from a first end portion of the driving shaft that is located close to the opening of the second passage in the axial direction of the driving shaft protrudes from the housing, and is connected to a member for driving the driving shaft. (12) According to further another configuration, in any of the above-described configurations, the second passage extends along one straight line. (13) According to further another configuration, in any of the above-described configurations, an area of the cross section of the first passage reduces as the first passage extends from the beginning portion to the termination portion. (14) According to further another configuration, in any of the above-described configurations, the second passage extends in a direction different from a direction in which the first passage extends. An area of an opening of the second passage at the termination portion of the first passage is equal to or smaller than an area of the first passage in cross section taken at a portion of the opening of the second passage at the termination portion of the first passage that is located closest to the beginning portion of the first passage, and is equal to or larger than an area of the first passage in cross section taken at a portion of the opening of the second passage at the termination portion of the first passage that is located farthest from the beginning portion of the first passage. (15) According to further another configuration, in any of the above-described configurations, the housing includes a housing main body including a recessed portion containing the pump element, a cover closing an opening of the recessed portion, a first fixation portion for fixing the cover to the housing main body, and a second fixation portion for fixing the housing to another member at a different position from the first fixation portion. (16) Further, from another aspect, a pump configured to pressurize and discharge sucked fluid, according to one configuration thereof, includes a housing, a shaft rotatably supported on the housing, and a pump element contained in the housing and coupled with the shaft. The housing contains therein an intake passage for introducing the fluid from outside the housing to the pump element, and a discharge passage for discharging the fluid pressurized by the pump element to outside the housing. The discharge passage includes a first passage extending around one straight line and including a beginning portion on one side where the pump element is located, and a termination portion. The first passage is shaped in such a manner that an area of a cross section thereof perpendicular to the straight line gradually reduces as the first passage extends from the beginning portion toward the termination portion. The discharge passage further includes a second passage connected to the termination portion of the first passage and opened to outside the housing. (17) According to another configuration, in the above-described configuration, the straight line extends along an axis of the shaft. A dimension of the first passage in a rotational direction of the shaft is larger than a dimension of the first passage in a radial direction of the shaft. (18) Further, from another aspect, a pump configured to pressurize and discharge sucked fluid, according to one configuration thereof, includes a housing and a pump element rotatably contained in the housing. The housing includes an intake passage for introducing the fluid to the pump element, and a discharge port extending around a first straight line in parallel with a rotational axis of the pump element. The fluid pressurized by the pump element is introduced into the discharge port. The discharge port has a flattened shape elongated in a rotational direction of the pump element in cross section perpendicular to the first straight line. The housing further includes a discharge passage for discharging the fluid introduced into the discharge port to outside the housing. The discharge passage includes a first passage connected to the discharge port and extending around a second straight line in parallel with the rotational axis of the pump element. The first passage has a flattened shape elongated in the rotational direction of the pump element in cross section perpendicular to the second straight line. The discharge passage further includes a second passage connected to the first passage and extending around a third straight line to be opened on an outer surface of the housing. (19) According to another aspect, in the above-described configuration, a shape of a connection portion between the discharge port and the first passage in cross section perpendicular to the rotational axis of the pump element changes continuously between the discharge port and the first passage. (20) According to another configuration, in any of the above-described configurations, the pump includes a driving shaft rotatably supported on the housing and configured to rotate the pump element. The second passage is opened on the outer surface of the housing on one side where the driving shaft is located with respect to the first passage. A second end portion of the driving shaft on an opposite side from a first end portion in proximity to the opening of the second passage protrudes from the housing, and power is transmitted from a driving source thereto. (21) According to further another configuration, in any of the above-described configurations, the housing includes a housing main body including a recessed portion containing the pump element, the discharge port, the first passage, and the second passage. The housing further includes a cover closing an opening of the recessed portion. (22) According to further another configuration, in any of the above-described configurations, the second passage perpendicular to the third straight line is circular in cross section. (23) A method for manufacturing a pump, according to one configuration thereof, includes forming a housing main body integrally by casting. The housing main body includes a recessed portion capable of rotationally containing a pump element, an intake port opened on the recessed portion, a discharge port opened on the recessed portion and extending along a rotational axis of the pump element while having a flattened shape elongated in a rotational direction of the pump element in cross section perpendicular to the rotational axis of the pump element, a first passage connected to the discharge port and extending along the rotational axis of the pump element while having a flattened shape elongated in the rotational direction of the pump element in cross section perpendicular to the rotational axis of the pump element, and a second passage connected to the first passage and extending linearly to be opened on an outer surface of the housing. The method further includes mounting the pump element into the recessed portion, and closing an opening of the recessed portion with a cover.

The present application claims priority under the Paris Convention to Japanese Patent Application No. 2017-135504 filed on Jul. 11, 2017.

The entire disclosure of Japanese Patent Application No. 2017-135504 filed on Jul. 11, 2017 including the specification, the claims, the drawings, and the abstract is incorporated herein by reference in its entirety.

REFERENCE SIGN LIST

-   -   1 pump     -   3 housing     -   4 driving shaft     -   40 axis     -   5 rotor (pump element)     -   6 vane (pump element)     -   11 intake passage     -   110 intake port     -   12 discharge passage     -   12A first passage     -   12A1 beginning portion     -   12A2 termination portion     -   12B second passage     -   120 discharge port 

1. A pump configured to suck and discharge fluid, the pump comprising: a housing; a driving shaft rotatably supported on the housing; and a pump element contained in the housing and configured to be rotated by the driving shaft, wherein the housing contains therein an intake passage to which the fluid is introduced from outside the housing, an intake port configured to guide the fluid from the intake passage to the pump element, a discharge port to which the fluid is introduced after being pressurized by the pump element, and a discharge passage configured to discharge the fluid delivered from the discharge port to outside the housing, wherein the discharge passage includes a first passage including a beginning portion connected to the discharge port and a termination portion, the first passage extending as far as the termination portion around one straight line, and a second passage connected to the termination portion of the first passage, the second passage being opened to outside the housing, and wherein a shape of the first passage in cross section taken along a direction perpendicular to the straight line continuously changes from the beginning portion to the termination portion.
 2. The pump according to claim 1, wherein, a cross-sectional shape of a connection portion between the discharge port and the beginning portion changes continuously between the discharge port and the beginning portion.
 3. The pump according to claim 1, wherein the straight line extends along an axis of the driving shaft.
 4. The pump according to claim 1, wherein the housing includes a housing main body including a recessed portion, the recessed portion being a bottomed cylindrical recessed portion extending around an axis of the driving shaft, the recessed portion containing the pump element, and a cover closing an opening of the recessed portion, and wherein the discharge port is opened on a bottom surface of the recessed portion in an axial direction of the driving shaft.
 5. The pump according to claim 4, wherein the discharge port extends along an axis of the driving shaft.
 6. The pump according to claim 1, wherein a dimension of the discharge port in a rotational direction of the driving shaft is larger than a dimension of the discharge port in a radial direction of the driving shaft, and wherein a dimension of the first passage in the rotational direction of the driving shaft is larger than a dimension of the first passage in the radial direction of the driving shaft.
 7. The pump according to claim 6, wherein the first passage is disposed on a front side in the rotational direction of the driving shaft with respect to the discharge port.
 8. The pump according to claim 6, wherein at least a part of a wall on an outer side in the radial direction of the driving shaft, among walls forming an inner periphery of the discharge port, is located on the outer side in the radial direction of the driving shaft with respect to a circular arc, the circular arc being centered at the axis of the driving shaft, the circular arc passing through an end on the outer side in the radial direction of the driving shaft in the beginning portion of the discharge port in the rotational direction of the driving shaft.
 9. The pump according to claim 1, wherein the housing includes a plate-like flattened portion, wherein a part of the first passage and the second passage are located inside the flattened portion, wherein the second passage is opened on a surface of the flattened portion on one side, and wherein a fixation portion for fixing a member connected to an opening of the second passage is provided at the flattened portion.
 10. The pump according to claim 1, wherein the second passage is opened to outside the housing at a position away from the driving shaft in the axial direction of the driving shaft.
 11. The pump according to claim 1, wherein a second end portion of the driving shaft on an opposite side from a first end portion of the driving shaft that is located close to the opening of the second passage in the axial direction of the driving shaft protrudes from the housing, and is connected to a member for driving the driving shaft.
 12. The pump according to claim 1, wherein the second passage extends along one straight line.
 13. The pump according to claim 1, wherein an area of the cross section of the first passage reduces as the first passage extends from the beginning portion to the termination portion.
 14. The pump according to claim 1, wherein the second passage extends in a direction different from a direction in which the first passage extends, wherein an area of an opening of the second passage at the termination portion of the first passage is equal to or smaller than an area of the first passage in cross section taken at a portion of the opening of the second passage at the termination portion of the first passage that is located closest to the beginning portion of the first passage, and is equal to or larger than an area of the first passage in cross section taken at a portion of the opening of the second passage at the termination portion of the first passage that is located farthest from the beginning portion of the first passage.
 15. The pump according to claim 1, wherein the housing includes a housing main body including a recessed portion containing the pump element, a cover closing an opening of the recessed portion, a first fixation portion for fixing the cover to the housing main body, and a second fixation portion for fixing the housing to another member at a different position from the first fixation portion.
 16. A pump configured to pressurize and discharge sucked fluid, the pump comprising: a housing; a shaft rotatably supported on the housing; and a pump element contained in the housing and coupled with the shaft, wherein the housing contains therein an intake passage for introducing the fluid from outside the housing to the pump element, and a discharge passage for discharging the fluid pressurized by the pump element to outside the housing, and wherein the discharge passage includes a first passage extending around one straight line and including a beginning portion on one side where the pump element is located, and a termination portion, the first passage being shaped in such a manner that an area of a cross section thereof perpendicular to the straight line gradually reduces as the first passage extends from the beginning portion toward the termination portion, and a second passage connected to the termination portion of the first passage and opened to outside the housing.
 17. The pump according to claim 16, wherein the straight line extends along an axis of the shaft, and wherein a dimension of the first passage in a rotational direction of the shaft is larger than a dimension of the first passage in a radial direction of the shaft.
 18. A method for manufacturing a pump, comprising: forming a housing main body integrally by casting, the housing main body including a recessed portion capable of rotationally containing a pump element, an intake port opened on the recessed portion, a discharge port opened on the recessed portion and extending along a rotational axis of the pump element, the discharge port having a flattened shape elongated in a rotational direction of the pump element in cross section perpendicular to the rotational axis of the pump element, a first passage connected to the discharge port and extending along the rotational axis of the pump element, the first passage having a flattened shape elongated in the rotational direction of the pump element in cross section perpendicular to the rotational axis of the pump element, and a second passage connected to the first passage and extending linearly to be opened on an outer surface of the housing; mounting the pump element into the recessed portion; and closing an opening of the recessed portion with a cover. 